A new message stating: "Rendering required files" has started consistently appearing when I press the "play" button or spacebar to play my video even though I am not aware of any clips that need rendering. This is followed by brief appearance of a progress bar which completes quickly and the video starts playing. I have not seen this message before. Does anyone know what this means? Do I need to clean up some files on the computer?

It could be a lot of things -- and the more detail you can give us, the more likely we can help you. In fact, a screen capture posted to this forum could be very helpful. Meantime:

1) Do you see red lines above the clips on your timeline? If so, press Enter to render your timeline. (The red lines will turn green.)

2) What model of camcorder is your video coming from and what format and resolution is it?

3) When you started your project, which project settings did you select? If you've selected the correct settings for your video, you will not see red lines above your clips when you add them to your timeline. Is this the case in your project?

4) When you capture your video or add your video to your project, do you allow you project to completely conform the video before you begin editing?